Magnetic recording medium and its manufacturing process

Abstract

A magnetic recording medium, comprising; a 2-layer film formed on a glass disk substrate as an under layer composed of an amorphous oxide or NaCl oxides like a NiO or CoO and the like, or any soft magnetic oxide of Mn-Zn ferrite, Ni-Zn ferrite and the like, or a combination of those 2 materials; a magnetic recording medium formed thereon composed of a Co ferrite perpendicular magnetic film of a columnar structure; and a structure formed thereon with a lubricant layer medium. This magnetic recording medium is used for a magnetic rigid disk apparatus. The substrate is made by press-molding the glass plate at a high temperature. The under layer film and Co ferrite film are composed of vapors of organic material compounds and oxygen as their raw materials, and made by a plasma assisted CVD method.

What is claimed is 
     
       1. A magnetic recording medium comprising: a glass substrate disk;   an under layer formed on at least one surface of the glass substrate disk, said under layer comprising a layer of a spinel crystal structured magnetic iron oxide layer laminated on a layer of a sodium chloride crystal structured oxide layer, said spinel crystal structured magnetic iron oxide having a spinel crystal structure as determined by X-ray diffraction and comprising an iron oxide containing at least one element selected from the group consisting of zinc, manganese and nickel, and said sodium chloride crystal structured oxide having a sodium chloride crystal structure with crystal orientation in a <100> direction perpendicular to the surface of the glass substrate as determined by X-ray diffraction and containing at least one oxide selected from the group consisting of NiO, CoO and MnO;   a layer of a ferromagnetic Co-containing iron oxide formed on a surface of the under layer in the form of columnar grains which are densely arranged perpendicularly to the surface of the under layer, said ferromagnetic Co-containing iron oxide having a spinel crystal structure with crystal orientation in a <100> direction perpendicular to the surface of the under layer as determined by X-ray diffraction; and   a lubricant layer formed on the layer of the ferromagnetic Co-containing iron oxide;   wherein the under layer is different from the layer of the ferromagnetic Co-containing iron oxide.   
     
     
       2. A magnetic recording medium as claimed in claim 1, in which the glass substrate disk is a disk-shaped glass substrate produced by press molding a heated glass material.